The present invention relates to a tire pressure warning system for warning an occupant of a vehicle that an air pressure is reduced, in the event that the air pressure of a tire of the vehicle is lower than a predetermined pressure value.
In recent years, in vehicles such as automobiles, the tire pressure warning systems have been widely used. The tire pressure warning systems monitor the air pressure of each tire and warn the occupant of a reduction in air pressure in the event that the air pressure drops remarkably. In the tire pressure warning systems, there are provided sensors for detecting a rotational speed of each wheel on which the tire is mounted, and the air pressure of each tire is calculated by comparing the rotational speeds of the respective wheels so detected according to running conditions of the vehicle.
Then, when the air pressure of at least one of the respective tires becomes lower than a running inhibition tire pressure that is set in advance, the occupant is warned of a reduced air pressure occurring in any one of the tires using an indicator installed in a passenger compartment, whereby the occupant can restore the reduced air pressure to its original pressure value before the normal running eis interfered.
The above tire pressure warning systems are disclosed, for example, in JP-A-10-512515.
Incidentally, it is known that the fuel consumption of the vehicle is largely affected by the air pressure of the tire as a rolling resistance of the vehicle increases, when the air pressure of the tire is reduced. With the aforesaid tire pressure warning system, however, the occupant is warned of only information regarding the running inhibition tire pressure that is required for the normal running of the vehicle. Namely, it will be more convenient if the occupant can be warned of not only an information regarding the normal running of the vehicle but also information regarding the fuel consumption of the vehicle.